1. Can you email to individuals/several people using group.io?
You, a moderator of the group, can checkmark members in the Members list and use the Send Message item in the Actions menu to send to just those members. You can use the Member Notices feature in the Settings page of your group to create and maintain a set of stock messages to select from when you send.
You, a member of the group, can click the Email button on an individual member's Directory entry, if the Directory is available to the group members (that's a group option) and if the member in question has made their profile available in the directory (that's a subscription option). In this case you won't see the other member's email address unless they reply to you, but yours will be in the From field of the message you send to them.
And, as Frances mentioned you, a member, can make a Private reply to a member's post. Same rule as above, you don't see their address unless they reply to you, but your address is in the From field of the message you send. Same thing if the group's Reply To is set to Sender instead of to Group.
And of course, you can use your email service to send messages to anyone whose address you have. If you subscribe to individual messages you'll receive other member's addresses in the From field of messages they post to the group
2. If you receive an email in your personal email and you want to email to the group.io distribution list are you able to do so. If you can how will this be done?
If you mean an email that didn't come from the group, you'd have to use your email interface to forward that message to the group's posting address. How you do that depends on your email interface.